Add comprehensive search and timeline filtering features

New Features:
- Search dialog (Ctrl+S): Find users, hashtags, and posts across the fediverse
- Timeline filtering (Ctrl+Shift+F): Filter content by type, media, and keywords/emojis
- Keyword/emoji blocking: Hide posts containing specific text or emojis
- Background search processing with tabbed results display
- Real-time filter application with accessible interface

Implementation:
- SearchDialog: Tabbed interface for users/posts/hashtags with background worker
- TimelineFilterDialog: Comprehensive filtering options with keyword management
- Enhanced TimelineView with content filtering logic and keyword blocking
- Menu integration and keyboard shortcuts for both features
- Full accessibility support with screen reader compatibility

Technical:
- Fixed import paths for proper module resolution
- Corrected Post/User object handling in search results
- Integrated filtering with existing timeline data flow
- Added proper method calls (from_api_dict vs from_api_data)

Documentation:
- Updated README.md with detailed feature descriptions and keyboard shortcuts
- Enhanced CLAUDE.md with implementation notes and development status
- Added comprehensive usage instructions for both search and filtering

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -429,6 +429,8 @@ Due to Qt's visual display synchronization, thread collapse may require double-o
 - **Ctrl+F**: Favorite selected post
 - **Ctrl+C**: Copy selected post to clipboard
 - **Ctrl+U**: Open URLs from selected post in browser
+- **Ctrl+S**: Open Search dialog for users, hashtags, and posts
+- **Ctrl+Shift+F**: Open Timeline Filters dialog
 - **Ctrl+Shift+E**: Edit selected post (your own posts only)
 - **Shift+Delete**: Delete selected post (your own posts only)
 - **F5**: Refresh timeline
@@ -552,6 +554,12 @@ verbose_announcements = true
 - **Social Actions**: ✅ Follow/unfollow, block/unblock, mute/unmute from profile viewer
 - **Post Editing**: ✅ Edit your own posts and DMs with proper local/federated ownership detection
 
+### Recently Implemented Features
+- **Search Functionality**: ✅ Comprehensive search for users, hashtags, and posts with accessible interface
+- **Timeline Filtering**: ✅ Filter home timeline by content type (replies, boosts, mentions) and media
+- **Search Dialog**: ✅ Dedicated search interface with tabbed results and background processing
+- **Filter Dialog**: ✅ Timeline filter configuration with real-time application
+
 ### Remaining High Priority Features
 - **User Blocking Management**: Block/unblock users with dedicated management interface
 - **User Muting Management**: Mute/unmute users with management interface